The Factor V Leiden test is a blood test that checks for the Factor V Leiden mutation.
Factor V (F5) is protein in the blood clotting system that enables various metabolic processes which cause blood clotting. When functioning normally, Factor V helps the clotting system form clots that stop abnormal bleeding throughout the body. It does this by serving as a helper (cofactor) in a clotting process that allows factor Xa to turn on prothrombin. The activation of prothrombin enables the formation of the matrix (fibrin) of the clot.
To stop Factor V's activity when clotting is no longer needed, the body releases a special protein called activated protein C (APC) which attaches to the Factor V protein and blocks its activity.
Factor V Leiden is a genetic mutation that affects the body's ability to regulate the Factor V protein. When people have this mutation, the protein that typically shuts down Factor V's clotting activity (APC) is impaired, leading to unregulated Factor V activity. Unregulated, Factor V becomes overactive, leading to excessive blood clotting. Known as a hypercoaguable state, Factor V Leiden results in more blood clots (typically in the veins). Unnecessary clots in the veins can travel circulate around the body and cause major problems such as a stroke, pulmonary embolism or heart attack.
A Factor V Leiden mutation should be suspected in anyone who has a blood clot without the typical risk factors. People who have had multiple clots without risk factors are at high risk and should undergo a Factor V Leiden blood test. Additionally people with a family history of clotting should also get this Factor V test.
Currently, there is no cure for Factor V Leiden thrombophilia. People who have the F5 genetic mutation and are having symptoms are typically treated with anticoagulants (blood thinners) such as heparin but it depends on the clinical circumstance. Women with the Factor V Leiden mutation who wish to get pregnant should do so in active consultation with a specialist as the risk of a clot during pregnancy in women may be up to seven times higher.
While Factor V Leiden is an autosomal dominant genetic disorder, not everyone who has the mutation expresses the problem with the characteristic clotting disorder. It is thought that the variability in symptoms is due to the number of F5 mutations, other genetic abnormalities, and the number of clotting risk factors the person has. Factor V Leiden mutations are common in people of European descent. In fact, data suggests that up to 8 percent of the Caucasian population in North America and Europe might have Factor V Leiden. The genetic mutation was discovered in the mid 1990s is named after a Dutch city of Leiden.
Last updated April 17, 2018. Given the evolving nature of medicine and science, this information might not be accurate and should not be construed as medical advice or diagnosis / treatment recommendations. Please consult a licensed medical provider if you have additional questions.